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XyZspineZyX
06-19-2003, 06:50 PM
In most reference books "initial climb rate" is listed in performance statistics. Exactly what does this refer to? Is this number substantially different from sustained rate of climb. Are the main factors in climb rate power, weight and drag? How important is the drag factor in sustained climb?

Comparing two specific aircraft in FB:

190A4: Power: 1550hp, Weight: 3989k, P/W ratio: .388
P39N1: Power: 1200hp, Weight: 3714k, P/W ratio: .323

Both of these a/c have similar climb rates in FB. Does the P-39 benefit greatly from its excellent aerodynamics in sustained climb? Do aerodynamics effect initial or sustained climb rate more?

Thanks for any help with this question.

faust

XyZspineZyX
06-19-2003, 06:50 PM
In most reference books "initial climb rate" is listed in performance statistics. Exactly what does this refer to? Is this number substantially different from sustained rate of climb. Are the main factors in climb rate power, weight and drag? How important is the drag factor in sustained climb?

Comparing two specific aircraft in FB:

190A4: Power: 1550hp, Weight: 3989k, P/W ratio: .388
P39N1: Power: 1200hp, Weight: 3714k, P/W ratio: .323

Both of these a/c have similar climb rates in FB. Does the P-39 benefit greatly from its excellent aerodynamics in sustained climb? Do aerodynamics effect initial or sustained climb rate more?

Thanks for any help with this question.

faust

XyZspineZyX
06-19-2003, 09:00 PM
Climb performance is usually measured at sea level, on a standard day, and usually at a specified loading which is typically max gross, or max combat weight. Altitude does have a dramatic effect on climb performance, though this is not by a fixed amount, and there are many factors that influence it. Propeller efficiency goes down in "thinner" air in the same way that a wing's ability to generate lift does, so static thrust would be less, and lift/drag ratio would decrease as well. The powerplant itself is also to blame. In most normally aspirated aircraft (not turbo or supercharged) their sea level climb performance may be twice their climb performance at a pressure altitude of as low as 6,000 feet. There is some standardization in the flight profile that these numbers are gathered for comparisons sake, though the numbers listed in initial climb are generally higher than you would ever see in flight at max gross weight.

Here is an excerpt from a Cutlass RG POH I have on hand:

Conditions:
Flaps up
Gear Up
2700 RPM
Full Throttle
Mixture leaned above 3,000 feet
Cowl Flaps Open
Weight 2650 lbs

Altitude(ft) Climb Speed(KIAS) Rate of climb(FPM)
Sea Level 84 855
2000 feet 83 755
4000 81 655
6000 80 560
8000 78 465
10000 77 370
12000 75 275


Aircraft with a Turbocharger/Supercharger are able to maintain their sea level performance at higher altitudes, which will help to maintain their their climbrate, and they often have a greater amount of excess power available than the aircraft listed above, but any increase in temperature, humidity, or a decrease in pressure will decrease climb performance.

S!
TX-EcoDragon
Black 1
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Message Edited on 06/19/0312:08PM by TX-EcoDragon

XyZspineZyX
06-19-2003, 09:06 PM
Very comprehensive answer, TX!

XyZspineZyX
06-20-2003, 12:46 AM
Thanks for the reply EcoDragon. /i/smilies/16x16_smiley-happy.gif